Molecular Regulation of Photoreceptor Cell Death

摘要 视网膜疾病是导致失明的主要原因，对患者和社会造成了巨大影响。一根根 视力低下的原因是光感受器细胞的死亡，这主要是由于正常的 这些细胞与视网膜色素上皮(RPE)之间的稳态相互作用。保存 光感受器(PR)的活性和功能仍然是一个关键的未得到满足的医学需求。Pr的含氧量最高 体内的消耗。脉络膜血管系统通过RPE提供这种需求--这一过程 需要紧密的对位和亲密的互动。视网膜-RPE动态平衡紊乱的时期可能是 预计会导致显著和快速的PR细胞死亡。但是，PR可以挺过RPE降低的时期 营养支持，为临床治疗视网膜疾病提供了机会之窗。目前有 没有维持PR活性或减缓细胞死亡率以延长这一治疗窗口的治疗选择。在……里面 我们发现，实验性视网膜脱离(RD)是PR-RPE动态平衡改变的有效模型 激活支持生存和死亡的两条途径。前者的例子包括释放保护性的 细胞因子和自噬的激活；而细胞死亡主要通过Fas介导的凋亡发生。一个 我们知识上的主要差距是我们不知道这些细胞保护性和 破坏细胞的途径。我们假设HMGB1和小胶质细胞代表关键的内在和外在 各自的影响。我们的初步数据有力地指出了已知的多功能蛋白的作用 高迁移率族蛋白1(HMGB1)在PR的内源性保护和先天免疫应答中的作用 强调公关。在特定的目标1中，我们将确定HMGB1在视网膜小胶质细胞PR死亡和激活中的作用 在RD之后和遗传性视网膜变性的模型中。我们的初步数据表明 HMGB1在视杆PR中对RD后的保护性自噬和小胶质细胞的激活起到保护作用。我们将调查 胞浆HMGB1在细胞自主激活和稳定促生存通路中的作用 PrS和释放的HMGB1的功能促进小胶质细胞的激活。在具体目标2中，我们将确定 小胶质细胞在RD后炎症反应和PR死亡中的作用。的相对贡献率 小胶质细胞和浸润性髓系白细胞以及免疫反应如何影响PR生存尚不清楚。 根据我们的初步数据，我们假设常驻小胶质细胞是RD的主要第一反应者， 小胶质细胞最初是保护性的，但最终转变为有害的炎症性表型。我们 进一步假设P38A-ULK1轴有助于这种位移。我们将定义和描述 应答RD的免疫细胞和检测靶向P38A和促进自噬是否具有保护性 研发。这项拨款中建议的工作将提供对监管机制的重要理解 光感受器细胞存活的控制。只有通过对这些基本过程的描述，我们才能 将能够开发有针对性的治疗方法来保持这些细胞的存活并改善患者的预后。

ABSTRACT Retinal diseases are a leading cause of blindness, tremendously impacting patients and society. A root cause of poor vision is death of the photoreceptor cell, which primarily results from disruption of the normal homeostatic interaction between these cells and the underlying retinal pigment epithelium (RPE). Preserving photoreceptor (PR) viability and function remains a critical unmet medical need. PRs have the highest oxygen consumption in the body. The choroidal vasculature supplies this demand through the RPE – a process that requires close apposition and intimate interaction. Periods of disrupted retina-RPE homeostasis might be expected to result in marked and rapid PR cell death. However, PRs can survive periods of reduced RPE nutritional support, resulting in a clinical window of opportunity for treating retinal disease. Currently there are no therapeutic options to maintain PR viability or slow the rate of cell death to extend this treatment window. In experimental retinal detachments (RD), a validated model of altered PR-RPE homeostasis, we have found activation of both pro-survival and death pathways. Examples of the former include the release of protective cytokines and activation of autophagy; whereas cell death occurs primarily through Fas-mediated apoptosis. A major gap in our knowledge is that we do not know the upstream activators of these cytoprotective and cytodestructive pathways. We hypothesize that HMGB1 and microglia represent key intrinsic and extrinsic influences, respectively. Our preliminary data strongly point towards a role for the multifunction protein known as High-Mobility Group Box 1 (HMGB1) in the intrinsic protection of PR and the innate immune response to stressed PR. In Specific Aim 1 we will define the role of HMGB1 in PR death and activation of retinal microglia after RD and in a model of inherited retinal degeneration. Our preliminary data connects the upregulation of HMGB1 in rod PR to protective autophagy and the activation of microglia following RD. We will investigate the function of cytosolic HMGB1 in cell-autonomous activation and stabilization of pro-survival pathways within PRs and the function of released HMGB1 to promote microglial activation. In Specific Aim 2 we will determine the role of microglia in the inflammatory response and PR death following RD. The relative contributions of microglia and infiltrating myeloid leukocytes and how the immune response affects PR survival are not clear. Based on our preliminary data, we hypothesize that resident microglia are the major first responders to RD, and that microglia are initially protective but eventually shift to a detrimental inflammatory phenotype. We further hypothesize that the p38a-ULK1 axis contributes to this shift. We will define and characterize the immune cells responding to RD and test if targeting p38a and promoting autophagy are protective following RD. The work proposed in this grant will provide a critical understanding of the mechanisms regulating the control of photoreceptor cell survival. It is only through the delineation of these fundamental processes that we will be able to develop targeted therapies to keep these cells alive and improve patient outcomes.